This invention relates to a simple apparatus and method for securing a steering wheel to a steering shaft, and further to a method and apparatus for preventing theft of the steering wheel.
In the prior art, steering wheels have traditionally been attached to a steering shaft prior to attachment of the air bag. Typically, the steering wheel was attached to the steering shaft by a bolt or a nut if the shaft is threaded. The air bag was then attached to the steering wheel module which included a cover, air bag and inflator.
More recently, there has been an effort to produce so-called xe2x80x9cmodularxe2x80x9d steering wheel and air bag assemblies. These assemblies use attachment techniques that allow the combined air bag module and steering wheel to be attached to the steering shaft as a pre-assembled modular unit.
In general, the prior art methods of attaching modular steering wheel assemblies to the steering shafts have been complex. Further, the methods have been relatively expensive, bulky and inelegant. Generally, the attachment methods rely on threaded connections between the steering shaft and the steering wheel hub. Typically, some form of a threaded member is driven relative to the hub and steering shaft to drive the hub onto the steering shaft.
These connections have typically been driven from the side of the hub, and have required access to be provided to the threaded member. Air bag theft is becoming an increasing problem. With modular steering wheel assemblies, there is an increased likelihood of theft of the steering wheel. With the prior art modular steering wheel proposals, since there has needed to be access to the threaded member, there is also access for a thief which would facilitate the removal of the steering wheel. This is, of course, undesirable.
In a disclosed embodiment of this invention, the steering wheel hub is attached to the steering shaft by providing the steering shaft with a slot extending from an end of the shaft, and leading into an enlarged securement space. A first securement member extends across a bore in the hub, and is received to draw a second securement member into the bore. The first securement member is preferably of a relatively small dimension, and fits through the slot in the steering shaft. The second securement member is preferably of a greater dimension, and does not fit through the slot. When the hub is placed on the steering shaft, the first securement member passes through the slot and into the enlarged space. The first securement member then draws the second securement member into the space. The second securement member thus locks the steering shaft onto the hub member. Tapered interface surfaces between the steering shaft and hub are forced together to provide a xe2x80x9cwedge lockxe2x80x9d, as described below.
The present invention thus provides a secure connection in a relatively small space.
In a preferred embodiment, the first securement member is externally threaded and the second securement member is internally threaded. The second securement member is preferably also tapered from an end remote from the space, and becoming smaller toward an end adjacent the securement space. This tapered surface rides along a mating tapered surface within the steering shaft. Thus, as the second securement member moves into the space, it forces the hub downwardly onto the shaft such that a wedge lock occurs. After connection, should one of the first or second securement members come loose or break, there is still a secure connection from the wedge lock.
In a further feature of this invention, a removal portion extends within the hub and across an upper surface of the steering shaft. The removal portion is preferably also provided by a threaded removal member and a tapered removal member. The taper action is reversed from the securement members such that as the threaded removal member draws the tapered removal member across an end surface of the steering shaft, the hub is forced upwardly off of the shaft, breaking the wedge lock. The first and second securement members preferably must be released or removed before the removal members can break the wedge lock.
The two structures (i.e., securement and removal) in combination provide a very inexpensive, compact, yet reliable way of securing and removing the steering wheel from the steering shaft. The structures provide improvements over the prior art methods for securing modular steering wheel and air bag assemblies to steering shafts.
In a further feature of this invention, the steering shaft is received within a fixed outer housing. The fixed outer housing has slots which provide access to the securement members in the hub. The slots are thus utilized to allow the steering wheel to be secured to the steering shaft.
The removal structure preferably is also aligned with an access opening. The access opening for the removal structure may be permanently accessible. To remove the wheel, the removal structure is actuated to break the wedge lock. However, unless the securement structure has been previously removed, the removal structure cannot remove the wheel as the securement structure prevents movement of the steering wheel relative to the steering shaft.
The slots on the outer housing are selected such that when the steering shaft is locked, as is the case when the ignition keys are removed from the vehicle, the securement members in the hub are not aligned with the slots in the outer housing. Thus, a thief does not have easy access to the securement location on the steering wheel, and theft of the steering wheel and air bag is less likely.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.